Transparent film



Patented Dec. 1930 UNITED STATES PATENT orrica CLARENCE E. GREIDBB, f LAKEWOOD, OHIO, ASSIGNOB TO NATIONAL CARBON (20.,

' INC A CORPORATION 0] NEW YORK TRANSPARENT mu m Drawing.

My invention relates to transparent materials, and particularly to such material, adapted to the transmission of light within the visible spectrum and a definite portion of the ultra-violet li ht spectrum. It has for one of its objects t e provision of a new and useful material for the glazing of windows,

for light-filters, and such like purposes, to transmit all but the extremely short wave portion of the ultra-violet rays, or for other purposes where a light filter having such a transmission is useful.

It is known that certain unsaturated compounds such as vinyl acetate, vinyl chloride, etc., when properly treated are polymerized into solids which are of good strength, in-

soluble in most fluids, optically clear, and

transparent to the visible spectrum. I find that polymerized vinyl acetate and its homoao log'ues, .are transparent not only to the visible spectrum but also to the ultra-violet spectrum down to a wave length of about 2900 Angstrom units, that shorter wave lengths are absorbed, and that the cut-off at this point is quite sharp, and constant.

In practicing my invention, I produce a filnr of the polymerized vinyl compound by any convenient means, which may be composed of a polymerized vinyl compound, as the acetate, alone, or may contain other vinyl, or other unsaturated compounds as well as the usual, diluents and saturated compounds, and may, if desired, include a wire mesh, a woven fabric, or other suitable reinforcing means for the provision of additional strength. .The material so prepared has a high transmission for all of the visible spectrum and for the ultra-violet spectrum having wave lengths greater than about 2900 Angstrom units, and absorbs the wave lengths shorterthan about 2900 Angstrom units.

The film of my invention is particularly adapted to the glazing of windows, because of its high strength, and resistance to weathering as wellas its flexibility and elasticity. It is likewise highly resistant to mischances which injure glass windows. It transmits the 1 beneficial ultra-violet rays which are ab- CQ sorbed by ordinary window glass. Accord- Application ma m 2, i928. semi'ro. 290,047.

ingly it is highly desirable for the glazing of windows in such locations as chlldrens nurseries, hospitals, greenhouses, and any place where it is desirable that livingthings shall have the benefit of the helpful ultra violet radiation.

The light transmission, and the cut-ofi of the vinyl acetate film are approximately the same as the transmission and cut-off of the earths atmosphere. Accordingly, a window glazed with the film of my invention interposes substantially no obstruction to the light radiation that is transmitted through the earths atmosphere. In this respect the film of my invention is fundamentally different from other flexible glazing materials, all of which show transmissions and cut-ofi-difiering more or less widely from that of the at mo here. a

T e filter film of my invention has the very" highly advantageous properties, that the transmission and cut-o do not change materially with prolonged exposure to ultraviolet radiation. It is well-known that other filter materials are greatly injured and their is transmissions grossly changed by rolonged exposure to such radiation. I find y experiment that exposure of the film of vinyl acetate for many hours to a high intensity of radiation, both ultra-violet and visible, results in" no material change in its ultra-violet transmission, While such films as cellulose acetate or other organic ,fihns which transmit ultraviolet, when similarly exposed, show a rapid change in transmission and a rise of the cut off point to 3200 Angstrom units, or above.

Another aspect of my invention thus comprises the combination of a source of light producing a wide range of -ultro-violet-radia; tion, with the filter film of my invention, whereby radiant energy closely comparable in spectrum" distribution to normal sunlight is obtained.

The filter of my invention is particularly advantageous in the artificial production of light corresponding to clear mountain sun; light. While the earths atmosphere 'tran'fs- -mits substantially all of the radiation having a wave'lengthgreater' than Kngstro'm units, the resence in it of small amounts of ating therewith comprising a film of-vinyl smoke'or ust causes the air to absorb most my invention with a suitable light source of the ultra-violet radiation. Thus inlfa bitants of smoky regions are freguentlyi' deprived of much of the helpful e ects of the ultra-violet radiation. This loss may be minimized by the substitution of artificial radiation containing the desired wave lengths from an appropriate source. In connection with such use the filter of my invention is of great value. Artificial sources which emit light highiin ultra-violet rays, such as carbon arc lamps trimmed with carbons treated with "certain of the metals, or the mercury arc in quartz tubes, yield not only visible radiation, but radiation extending far down the speetrum, to wave lengths shorter than 2900 Angstrom units. Where a substitute for sunlight for certain medicinal applications is esired, it is necessary that the wave lengths shorter than 2900 Angstrom units be absorbed from such artificial sources, in order to producea radiation as nearly as possible the same. as the radiation received from the sunthrough the atmosphere. This, result is obtainable by the combination of the filter of emitting quantities of ultra-violet rays.

I A convenient means of application of the filter of myinvention is in the form of a curftain beforethe light source, a suflicient distance away to be safe from heat produced by the source... When so used the filter produces the desired character of radiation, and it shows a high durability and a high stability, since the transmission does not change upon prolonged exposure to the ultra-violet radia- 1 tion.

- By my invention I have thus produced a new and useful glazing material and light filter which has a transmission and cut-ofi of great value, which is of excellent mechanical strength, and which is of high durability, and resistance to change from exposure to the elements. V v

. The above disclosure shows but a limited number of embodimentaof my invention,

which may, however, be adapted to still other embodiments without-departure from the spirit thereof, and I desire therefore that only such limitations shallbe imposed upon acetate.

5. A light source comprising an illuminant reenforcing member incorporated therein, said filmhavinga radiation cut-01f at about 2900 Angstrom units and absorbing shorter wave lengths.

{7. A glazing material comprising a film of a vinyl compound reinforced with a woven material,having' a radiation cut-off at 2900 formed of avinyl compound and a reticulated I Angstromunits and absorbing shorter wave lengths. r

8. In combination an artificial source of ultra-violet radiation and a filter, transparent to-ultra-violet radiation to about 2900 Angstrom units and absorbing radiations of shorter wavelengths, comprising a .film of polymerized vinyl compound. r T 1 I In testimony whereof I afiix my signature;

CLAREN E E; GREIDER.

the appended claims as are stated therein or required by the prior art.

I I claim as my invention'i 1; A light filter comprising a film of a polymerized vinyl compound and areticulated member incorporated therein.

2. A light filter comprising a film of i merized vinyl acetate.

' 3. .A light filter comprising a film supporting means.

Y 4. In combination a source of light rich in tf oly f "'merized vinyl acetate and an incorporated I. 

